Telephone system



June 14, 1927..

1,631,981 L. F. PORTER TELEPHONE SYSTEM Filed July 31. 1925 umms 9 lnv enfor: 7 Leslie 5 Porfer Patented June 14, 1927. y

UNITED STATES PATENT OFFICE.

LESLIE F. PORTER, OF PASSAIC, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

This invention relates to telephone systems, and more particularly to unprovements in the connecting circuits used in toll switching systems whereby operators at toll switching centers establish connections between switching trunks or toll' lines.

In systems of this kind where Connections between subscribers located at widely distant points are desired, anumber of various types of connections may be made at the toll switching centers or otiices. For example, a connection may be established from a calling subscriber at a local ofiice over a switching trunk to the toll office and from there over a long distancetoll line to another local office from which the called subscriber may be reached. In this type of connections it is not ordinarily necessary to include the usual repeater networks in the transmission line at the toll oflice. However, in some other types of connections, it is essential that repeater networks should be included at the toll ofiice for the well known purpose-of maintaining the proper trai'lsmission line efficiency. This inclusion usually essential for connections where the switching trunk incoming from a local oflice is unusually long or where the connec tions will extend through other toll ofiices over long distance toll lines in either or both directions. The toll operators cord circuits,switching trunks and tell lines; are usually so designed that in cases where no repeaters arcrequired, automatic changes will take place on the establishing of a connectionto exclude the repeater therefrom. On the other hand, in connections where repeaters are required these circuits will automatically act on the establishing of such connections to ll'lJlLlLlQtllt-t repeater.

It is an object of this invention to provide improved circuit arrangements in switching trunks, toll lines and universal toll operators cord circuits used in establishing connections of the above mentioned types.

Another object of the invention is to utilize alternating current in the supervisory control over such types of connections. To attain these and other objects of the invention. as will hereinafter appear, there is provided in accordance with one feature thereof means whereby the inclusion or omission oi? the usual repeaters in connections oi the above typeandthe performing of the usual. busy test may be under control of alternating current signals of different character. Such control is independent'of other supervisory functions performed during the establishing of such connections. a

Another feature resides in the provision of means whereby when a connection is established, between a switching trunk or a toll line and another toll line requiring a repeater, the cord circuit used in the connection is automatically controlled by alternating current signals to include a repeater n said cord circuits. On the other hand if the connection is extended between a switching trunk and a toll line that do not require the inclusion oi a repeater, a condition suitable for such a connection is automatically established or maintained in the cord circuit. Anotherbfeature of the invention is the provision of means whereby the alternat- 1ng current signals used for changing the conditions of thecord circuit as mentioned above are effective over the sleeve terminals of the jacks andplugs-in which the switch ing trunks, toll lines and cord circuits terminate.

Another feature of the invention resides in means whereby alternating current sig- 'nals' are used for actuating the usual busy test signals such alternating current signals being effective over the sleeve terminals of the. switching trunk or toll line tested and over the tip conductors of the cord circuit employed.

Another feature of the invention resides in the provision'of means whereby the'insertion of both the answering and calling plugs of a cord circuit into the jacks of the lines connected thereby is required before tion in the cord circuit is effected.

Another feature'of the invention resides in the provision of alternating current responsive relays for changing the conditions of the cord circuits which are common to a plurality of cord circuits. 7 The invention has been illustrated in the accompanying drawings in which Fig. 1

shows the incoming end of a switching trunk or toll line equipped to cause the inclusion of a repeater. the outgoing end of a toll line the. change in or maintenance of the. Condi- 7 service of a repeater.

this invention. Fig. 2 shows the incoming end of a switching trunk not arranged for the inclusion of a repeater when connected to the cord circuits shown in Fig. '1. Fig. 3 shows the outgoing end of a switching trunk or toll line that does not require the All of these'lines are also shown in accordance with this invention with means for performing the usual busy test employing alternating current signals.

The drawings show means wherebya connection may be established from a calling subscriber, connected through the opposite end 01' the switching trunk or toll line 1 at a distant exchange, over the cord circuit 2 at a toll oilice to the toll line 3 outgoing to a'distantexchange and from there to the called subscriber through the usual channels. A connection may also extend from the switching trunk 4 over the cord circuit 2 and the switching trunk or toll line 5; or from switching trunk 1- over the cord circuit 2 and the toll line 3 or switching trunk or toll line 5; or from toll line 3, or switching trunk or toll line 5 in the opposite direction to switching trunk or toll line 1', 'or switching trunk 4. I

In the type of connections mentioned above a switching trunk or toll line 1 and toll line 3 are assumed to be of such length as to require the inclusion of repeaters, and consequently are so arranged that when they are connected through cord c'ircuitQ, the repeater indicated by a box 6 is included in the transmission circuit between the two lines. (in the other hand, it a connection is desired between switching trunk 1 and switching trunk or toll line 5, which are assumed to be of such length as not to require the inclusion of repeaters, the cord circuit conditions will be such as to prevent the repeater 6 from being; included in the transmission line between the two lines. This latter effect will also be produced in the cord circuit if a connection is made between sliort line at one end, such as switching trunk 4t and a long line at the opposite end, such as toll line 3.

In order to make the application of the invention to these disclosures more clear, a detailed description will be made; first, a connection between switching trunk ortoll line 1 and the toll line 3 which require the usual repeater, and second, a connect-ion requiring no repeater such as between switching trunk and switching trunk or toll line 5.

Assuming then that the toll operator equipped with cord circuit 2 has been assigned or has selected, in the usual manner intoll line service, the switching trunk or toll line 1 for the establishment of a conn ecti on from a distant ofl'ice, the usual busy te'ft may be performed or not depending on the mannerin which the line 1 is appropriated. If the busy test is to be performed, the operator first actuates her talking key 9 and then touches the sleeve of jack 8 with the tip of plug 7. On the operation of key 9,'circuits for relays 10 and 11 are completed as follows: battery, lower windings of re lays 10 and 11 in parallel, closed upper outer contacts of relay 9, inalte-betore-break contacts of relay 12 to ground. This circuit is however only completed if relay 12 is in a released condition and the arrangement is such that it will be released as soon as the equipment below the dash-dotted line in the drawing, which is common to a plurality of cord circuits", is released from use with another cord circuit. This common equipment includes an operators telephone set, a busy test relay arrangement, alternating current responsive relays required for the inclusion of the repeater 6 with cord circuits and alternating current sources employed in this system. Relays 1.0 and 1.1 in operating open the tip and ring leads of the cord and include the balancing networks 13 and 14; in the opposite sides respectively of the repeater 6 so that when it is subsequently connected to the cord circuit, singing is prevented as is well known in the art. The operation of relays 10 and 11 also (.lOT'OS a circuit for relay 12 as follows: battery, winding ()1? relay 12, lower outer arn'iature and front contacts of relays 11 and 10 in series to ground. Relay 12 in operating opens the operating circuit'tor relays 10 and 11' at its make-before-break contact, but at tlie'saine time closes at its armature and front contact an obvious locking circuit for these two relays through their upper windings.

11'' it is found that the switching trunk 1 is engaged through a multiple jack at another position in a connection of the same type, relay 15 will be operated over a circuit as follows: battery, the supervisory lamp of the employed cord circuit at the other position corresponding to lamp 16 of cord circuit 2, normally closed contacts of a talking key corresponding to key 9, sleeve of the plug corresponding to plug 7, sleeve of a multiple jack of switching trunk 1, windingof relay 15 to ground. Consequently, when the tip of plug 7 comes in contact with the sleeve of jack 8 when the busy test is peittormei'l, a c"cuit as follows will be completed. From one side of the alter nating current sources 17 and 23 outer armature and front contact of relay 15. sleeve o'l jack 8 tip of plug 7, upper inner armature and front contact of relay 10, through rious common keys, such as a ringi and a splitting key, well known in the art and therefore merely indicated by a box ell, inner ari'i'iature and back contact of relay l9, alternating current responsive relay 1% to ground. Relay l8 responds to the particu- Ice current sources l7 sleeve of jack 26 if the toll line 3 relay 18 will operate and a busy test signal lair, alternating current from source 17 and closes a circuit to the usual busy test circuit at the operators telephone set conl'iected at (l. T. so that the operator will now receive the usual indication that the jack tested is winding of marginal relay 21, inner upper closed contacts of key- 9, sleeve terminals of plug 7 and jack 8, winding of relay to ground. This circuit causes the operation oi re ays 20 and 15. The operation of relay 20 closes an obvious circuit fo1.11elay 19, so that relay 19 in operating opens the connection for the busy test relay 18 and closes a connection for the alternating current responsiverelay '22 to the alternating and On the operation of relay 15, this circuit from the sources 1.7and 23 through the relay is completed as follows: one side ot the alternating cur rent sources 17 and 2S, outer armature and front contact of relay 1 5,sleeve terminals of jack 8 and plug 7 inner upper closed contacts of key 9, Winding of alternating current responsive relay 22, outer armature and ,l'ront contact of relay 19, to ground. Re-

lay 22 operates in response to the current from the particular alternating current source 23 and closes at its; armature and trout contact a circult for the inclusion of repeater 6 in the transmission circuit of cord circuit 2, as will be hereinafter described.

It will be understood that in accordance with standard toll 7 practice, the operator at this office has acquired throughthe usual means, the numbers of both the calling and called subscribers and while the calling subscribefls line is being connected to the switching trunk 1 through theusual B 0pcrators position at the distant office, this tell operator now connects her calling plug to jack26 of the toll line 3 leading to the oflice throughwhichy the wanted subscriber may be reached; Itshould be understood. also that a busy test of this toll line i 3 may be perforn'ied in the same manner as was the busy test of switching trunk 1. That is, on touclnng the tip ofplug 25 to is busy.

givcirto the operator. The insertion of plug 25 in jack 26 closes a circuit asfollows: battery, relay 27, marginal relay 28, closed contacts of key 9, sleeve terminals of plug 25 and jack 26, relay 29 to groundr This causes the operation of relays27 and 29 The operation of relay27 closes an obvious energizing circuit for relay 30 which in operatingremoves the busy test relay 18 from connectionwith the tip of the plug of key 9, respectively, to the tact of relay 32.

25 and closes a circuit to the alternating current sources 17 and 23 so that a circuit is now completed from ground, through the outer armature and front contact of relay 30, alternating current responsive relay 31, closed contacts of key 9, sleeve terminals of plug 25hnd jack 26, outer arinatiu'e and front contact of relay 29, to the opposite side of the alterlniting current sources 17 and 23. This circuit causes the operation or relay 31 in response to the current from source 23 and a circuit is thereby closed for the operation of, relay 32' as follows: battery,

winding of relay 32, closed contacts of key 9, armature and "front contact oi -alternatcurrent responsive relay 22 and armature and front contact of alternating current responsive relay 31 to ground. The op eration of relay 32 causes the leads from the repeater 6 to be connected to both sides of the cord circuit talking conductors, that is, a circuit will be completed from the inner upper and lower arniatnres and front 'contacts of the relay 32, through the repeater to the upper and lower make before break contacts of relay 32. -A circuit will also be closed at the upper outer armature and front contact of relay 32 to ground for the repeater (l to start it to function as iswell known in the art It should be understood that any well-known type of repeater cir' cuit may be used andtherefore no details of such a circuit has been shown, but merely represented by the box 6.

It should be noted that when the key 9 was operated a circuit was completed forrelay 35 and relay 361'as follows: battery, windings of these relays to closed contacts ground at '37 so that these relays were operated innnediately after the actuation of key- 9. The operation of these relays therefore provides a locking circuit for relay 32 over an obvious circuit to the lower outer armature andt'ront con- As is well known in stand ard toll practice'when the calling subscribers line has been connected through the B operators position at the distant o llice't'o the switching trunk 1, the conditiono't the sleeve circuit of jack 8 will change. That is, a low resistance path to ground will be provided for the sleeve through a resistance 38 iso that now the electrical character 01' the circuit tln'oughrelays 2(l-and 21 will be such as to cause the marginal relay 21 to ope ate. The operation of this marginal relay 21 closes a circuit through a low resistance to ground for the lamp 16' This lamp is now lighted to indicate to the operator at the cord circuit 2 that theswitching trunk is connected through to the calling subscribers line. In a similar manner the toll operator at cord circuit 2 may be notified, by the operator at the opposite end of the toll line 3 causing the lamp 39 to be lighted, that the the talking key 9 and the eilect or called subscribers line hasbeen connected through to the toll line 3, although the usual practice is that the operator at the distant ofiice transmits this information verbally to the toll operator and the information that the wanted subscriber has been called and is ready to receive the call. lVhen these indications have been received by the toll operator, she proceeds to ring the calling subscriber by operating the usual ringing key, not shown, but as stated may be included in the talking leads at the place indicated by the numeral 41. \Vhen the calling subscriber removes his receiver from the hook in answer to the ringing the condition of the sleeve of switching trunk 1 is changed so as to remove therefrom the resistance 38 to ground and thus cause relay 21 to release and thereby extinguish lamp 16 as an indi cation to the toll operator that the calling subscriber has answered the call.

The calling and called subscriber are now therefore connected respectively to the switching trunk 1 and the toll line 3 and it now merely remains for the toll operator to complete the connection between these two lines. She accomplishes this by releasing this operation is that the talking leads are connected through from plug 7 to plug 2:) through the repeater 6 by the release of relays 10 and 11. It will be noted that the sleeve connection from jack 8 and plug 7 is now extended directly to the lamp 16 and relay 35. Lamp 16, however, is not lighted at this time due to the resistance conditions on the sleeve circuit; but relay is maintained operated so that the locking circuits closed at the armature and front contacts of relays 35.nnd 3G for relay 32 are maintained and therefore relay 32 is held operated to maintain the repeater 6 in the circuit. Relays 20, 19, 27 and 30 are also released on the return o't' key 9 to normal. Upon the release of relays 10 and 11 the circuit for relay 12 is broken, so that the common equipment will now be in position to be used by any other cord circuit.

Conversation between the calling and called subscriber may therefore now begin and when the conversation ceases and the calling subscriber, for example, hangs up his receiver, lamp 16 will again become lighted as release indication to the operator at cord circuit 2. The toll operator may then break down the connection by removing her plugs 7 and 2-3, and relays 85., 36 and 32' are all returned to normal as well as the relays 15 and 29 at the incoming ends of switching trunk 1 and toll line 3.

It will be seen that in connection with the above type the fact that an alternating current source, such as 23, is connected to the sleeve circuits of jack '8 and jack 26 causes the operation of the common equipment and the operation of relay 32 to include the repeater 6 in the transmission circuit between the two lines.

If a connection is desired between a switching trunk, such as 4, and a switching trunk or toll line, such as 5, requiring no repeater, the busy test may be performed, in the same manner as described in the previous case, that is a busy test of switching trunk 4 may be performed through the outer armature and front contact of relay 15' which is operated when this switching trunk is busy and the busy tone from alternating current source 17 is connected with the sleeve of jack 8. The same operation will take place when a busy test is performed to ascertain the busy or idle condition of switching trunk or toll line 5 where the busy tone alternating current source 17" will be connected to the sleeve of jack 26 through the operation of relay 29'.

It switching trunk 4 and switching trunk or toll line 5 are idlc.the toll operator will first insert plug 7 into the jack 8 thus causing the operation of relays 15 and 20, which in turn, cause the operation of relay 19 to complete the tip lead through to the operators telephone set 0. T. As an alternating current source such as 23 is not conuected to the sleeve circuit of the switching trunk 4, relay 22 will not operate at this time nor will relay 31 operate when plug 25 is inserted in jack 26' as no alternating current source such as 23 is connected to the sleeve circuit of this jack. Consequently, the circuit for relay will .not be closed and the continuity of the talking leads between the plugs 7 and 25 will therefore not be disturbed except, of course, at the armature and contacts of relays 10 and 11 which relays will be inaintained operated until the release of key 9 when the connection will be cut through from the calling and called subscriber by the release of these relays. It is evident then that in this case, due to the fact that an alternating current source such as 23 is not connected to the sleeve circuits of the jacks 8' and 26 of these two lines, the cord circuit 2 will function so as not to include the repeater 6.

On the other hand, if a connection is desired between the switching trunk 4 and the toll line 3 it will be seen that the result of functioning of the cord circuit 2 will be the same. that isthe repeater 6 will not be included as in this case relay 22 will not operate so that the circuit for relay-32 will not be completed.

In connections extending from the oppo site direction the functions of the cord circuit will be the same for the three types of connections mentioned above. It may also be pointed out that the arrangement of the cord circuit 2 is such that it is immaterial how the plugs 7 and 2.) are used in a connection of this sort. That is, plug 25 may be used for answering a call, While plug 7 may be used for completing a through connection and vice versa.

What is claimed is:

1. In a telephone system, lines, cord circuits for interconnecting said lines; a plurality of alternating current sources associated with said lines, a busy signaling device common to said cord circuits, means responsive to current from one alternating current source for actuating said device When an engaged line is tested by a cord circuit, and means responsive to current from another alternating current source .for changing the condition of a cord circuit connected to a line.

2. In a telephone system, lines, a cord circuit for interconnecting said lines, a source of alternating current associated With each line, means responsive to said alternating current associated with one end of the cord circuit for preparing it for a change in, condition, and means associated with the other end of the cord circuit for completing the change in condition of said cord circuit. r

3. In a telephone system, lines, a cord circuit for interconnecting said lines, a source of alternating current associated With each line, means individual to the calling end of the cord circuit responsive to alternating current from a connected line, means individual to the called end of the cord circuit responsive to alternating current from a connected line, and means jointly responsive to said last mentioned two means for changing the condition of saidcord circuit.

In Witness whereof, I hereuntojsubscribe 

